Studio wall construction

C

Chadwick

New member
I am building a studio that will take a little more than half of the space in my garage. I am building a room within a room with a floating floor. I 'm removing the fold up garage door and replacing it with a wall that is like the other 3 existing garage walls. The distance between the outside of the new walls and the inside of the garage walls will be within inches on three sides and about 10 feet on one side. The garage walls are stucco with nothing on the inside(exposed studs). Which of the following methods should I use for construction the studio walls?

1. Single wall construction with insulation and drywall layers on both sides.
2. Staggered wall construction with insulation and drywall layers on both sides.
3. Single wall construction with insulation and drywall layers on only the inside.
4. double wall construction with insulation and drywall layers on both sides.

Using drywall on only the inside will allow a single large air space between the garage and studio walls as opposed to 2 air gaps between them. According to John Sayers wall STC chart a single air space is more effective. I tried to attach that chart to this thread but I couldn't figure it out.

I will install insulation in between the studs on the garage walls but I'm also wondering if I should cover with drywall layers as well.

According to that chart it looks like I shouldn't install any dry wall in between the inside of the garage wall and the outside of the studio wall and just leave the insulation exposed, but its hard for me to imagine that that would be more effective than double walling it and putting dry wall all over.

Thanks,
Chad
 
Chad, I'm very familiar with that chart, since I moderate the construction forum there - and I'm very glad you've done your homework and have pretty much already convinced yourself to do what will actually WORK instead of what SEEMS like it should work...

You hit the nail on the head about using only two leaves (centers of mass) in a sound wall. If your existing stud walls are still open, you have the least amount of work ahead of you that is possible in order to get some decent isolation.

The things that make for maximum effectiveness in sound wall construction are the amount of mass in each of two leaves, the mass (Pounds per Cubic Foot) of the in-wall insulation, 3 pcf being optimum, and the air gap between the two leaves of the wall. The more mass, the better - the wider air gap, the better - if one of the leaves can be de-coupled from the other, it helps several dB also - if you don't use acoustic-rated caulk and TOTALLY hermetically SEAL each and every joint/crack/hole/outlet, etc, then don't bother to do ANY of the above because it won't make enough difference to be worth the effort. It's amazing just how small a crack will lower the performance of a wall by 10-15 dB, sometimes even more.

In your case, the most effective way to soundproof your area on the three sides that will be close-coupled, (unless one of those is NOT next to a stucco wall with open studs) is to put a vapor barrier against the inside of the outer wall between the studs, then add two layers of sheet rock between each stud pair, sealing as you go with acoustic caulk (if there are any places where you can see light thru the wall, seal those first)

Then, however much air gap you can afford without giving up too much space, then the new frame with dense insulation (either 3" of 703, or Knauf equivalent, or mineral wool/rockwool between the new studs - put Resilient Channel perpendicular to the studs and two layers of sheet rock over that, being careful not to put any screws into the sheet rock over a stud just in case they're long enough to touch the stud and "short out" the channel - seal the cracks in the first layer of rock with acoustic caulk, offset seams on the second layer, leave 1/4" gaps at the floor, let the wallboard "sag" on the channel for about a week then caulk the perimeters with more acoustic caulk - This should be done AFTER taping/sanding/vacuuming the sheet rock.

Be sure to use ONLY screws that are designed for sheet rock installation, otherwise the channel won't hold and the wall will fail. If you can find square-drive screws instead of philips, do it.

On the dividing wall, you'll need to do BOTH sides of the frame - preferably either a staggered stud frame or preferably a double frame, or 6" steel studs with double sheet rock on each side, stuffed with spun fiberglas or 2-3" of the 3 pcf semi-rigid as in the other walls.

Your door(s) will be the weak link if your ceiling/floors are done as tight as the walls - if there's room, a sound lock would work best using something like two 36" exterior doors separated by at least 2 feet and the area between the doors FULLY absorbed with the same stuff you put in the walls. Don't neglect the area surrounding the doors, including the threshold - if the threshold is an aluminum extrusion, it needs to be FILLED with acoustic caulk before you install it. Doors are usually shimmed to fit the rough opening in a wall - this will leave huge gaps that also need to be totally sealed before any trim is applied.

If you pay loads of attention to detail and leave no tiny cracks un-caulked, building this way should get you anywhere from 50 to 60 dB of isolation. That means that if you're playing live with a band at 110 dB inside, a couple feet from the outer wall the sound level should be where most cities put the legal limit (I think most places want less than 60 dB, possibly 50 at the property line)

Here are a couple of really useful sites for construction info -

http://www.usgaction.com/handbook/toc.htm

http://www.usg.com/Design_Solutions/2_3_8_tableofcontent.asp

And here is a source of acoustic caulk, $7.50 per QUART tube, which is about TWICE what you'd pay if you can find it locally at a commercial insulation/drywall place - still, that equates to $2.50 a tube for the small, 10 oz size tubes and they DON'T WORK for long before developing hair-line cracks that weaken the sound performance of the wall -

http://www.acousticalsolutions.com/products/sealants/caulk.asp

If you're not planning on recording live bands, using acoustic drums, or having bass players with 1000-watt stacks, but instead doing mostly electronic music and mixing at the correct levels of around 85-90 dB, then you wouldn't need quite as much isolation. Unless of course you're into plaintive, acoustic guitar songs and your neighbor (like mine) is addicted to mowing his lawn.

I probably missed several points - hopefully the USG links will help with some of your questions, or come back here... Steve
 
On the dividing wall, you'll need to do BOTH sides of the frame - preferably either a staggered stud frame or preferably a double frame, or 6" steel studs with double sheet rock on each side, stuffed with spun fiberglas or 2-3" of the 3 pcf semi-rigid as in the other walls.

Thanks a lot for all your input Steve! I need to clear something up though. Are you talking about an isolation wall like between a live room and control room in the above statement or are you saying I should fill the existing studs with drywall, leave a space, build a second wall with drywall on one side, leave another space and then build a staggered stud wall in front of that?

Thanks again for all that. Now I will check those links you suggested.

Oh yeah one more thing. How do I change the fonts style, color and size like everyone does?

Chad
 
I'm definitely NOT saying you should build a bunch of walls - my comments re the staggered stud OR a double framed wall, were ONLY for the wall you mentioned having to build that WASN'T close to an outside wall. IF you're building a 2-room setup, then the control room wall should be double-framed with wallboard only on the outside of each frame, the two frames NOT touching each other in any solid way, and same for a control room window if you use one. YOu want the two leaves of a control room wall to be totally isolated physically from each other, including the glass - then, the surround between the two glasses should be absorptive so that the glasses can "bleed off" into the inner wall cavity for better isolation.

The only places I was talking about putting sheet rock between studs instead of ON them, were the outside walls that are already stucco. You would need more mass in the outer leaf before adding the inner frame with sheet rock/insulation.

At no time do you want more than two leaves, each with up to 3 layers of material, in any wall. Using any other design is just a waste of space, time and money.

If you're short on space and don't have quite as strict a need for sound proofing, you could build John's "inside out" walls and get absorption built in, but if you have the space a deeper air gap will help isolation quite a bit... Steve
 
Got it. Thanks again for all the help. I have a few more issues to post after I check again and make sure the answers haven't already been discussed in this forum and then It's time to start building.
Chad
 
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